title: Audiologic outcomes with the penetrating electrode auditory brainstem implant.
abstract: OBJECTIVE
  The penetrating electrode auditory brainstem implant (PABI) is an extension of auditory brainstem implant (ABI) technology originally developed for individuals deafened by neurofibromatosis type 2. Whereas the conventional ABI uses surface electrodes on the cochlear nuclei, the PABI uses 8 or 10 penetrating microelectrodes in conjunction with a separate array of 10 or 12 surface electrodes. The goals of the PABI were to use microstimulation to reduce threshold current levels, increase the range of pitch percepts, and improve electrode selectivity and speech recognition. PATIENTS AND PROTOCOL: In a prospective clinical trial, 10 individuals, all with neurofibromatosis type 2, received a PABI after vestibular schwannoma removal via a translabyrinthine approach. All study participants met strict requirements for informed consent as part of a Food and Drug Administration clinical trial. Approximately 8 weeks after implantation, PABI devices were activated and tested at our tertiary clinical and research facility. Mean follow-up time was 33.8 months.
  
  
  METHODS
  Using a single-subject design, we measured thresholds and dynamic ranges, electrode-specific pitch percepts, and speech perception performance at regular intervals.
  
  
  RESULTS
  Penetrating electrodes produced auditory thresholds at substantially lower charge levels than surface electrodes, a wide range of electrode-specific pitch sensations, and minimal cross-electrode interference and could be used in speech maps either alone or in combination with surface electrodes. However, less than 25% of penetrating electrodes resulted in auditory sensations, whereas more than 60% of surface electrodes were effective. Even after more than 3 years of experience, patients using penetrating electrodes did not achieve improved speech recognition compared with those using surface electrode ABIs. In patients with usable penetrating electrodes, City University of New York Sentence Test scores with sound and visual information were 61.6% in the PABI group and 64.7% in a surface ABI cohort (p = not significant).
  
  
  CONCLUSIONS
  The PABI met the goals of lower threshold, increased pitch range, and high selectivity, but these properties did not result in improved speech recognition.
authors.affiliation: House Ear Institute, Los Angeles, California 90057, USA. otto@hei.org
authors.forename: Steven R
authors.initials: SR
authors.lastname: Otto
authors.forename: Robert V
authors.initials: RV
authors.lastname: Shannon
authors.forename: Eric P
authors.initials: EP
authors.lastname: Wilkinson
authors.forename: William E
authors.initials: WE
authors.lastname: Hitselberger
authors.forename: Douglas B
authors.initials: DB
authors.lastname: McCreery
authors.forename: Jean K
authors.initials: JK
authors.lastname: Moore
authors.forename: Derald E
authors.initials: DE
authors.lastname: Brackmann
mesh_terms: D000328:Adult; D038262:Auditory Brain Stem Implants; D003056:Cochlear Nerve / Q000503:physiopathology; D003638:Deafness / Q000209:etiology / Q000601:surgery*; D004558:Electric Stimulation; D004566:Electrodes; D004867:Equipment Design; D005260:Female; D006310:Hearing Aids; D006320:Hearing Tests; D006801:Humans; D008297:Male; D008875:Middle Aged; D016518:Neurofibromatosis 2 / Q000150:complications*; D010898:Pitch Perception; D019736:Prostheses and Implants; D016896:Treatment Outcome; D055815:Young Adult